In-cell touch for LED

ABSTRACT

A touch screen having touch circuitry integrated into a display pixel stackup. The touch screen can include a transistor layer, an LED layer and a first layer. The first layer can operate as an LED cathode during a display phase and as touch circuitry during a touch sensing phase. The transistor layer can be at least partially utilized for transitioning between the display phase and the touch sensing phase. The touch screen can be fabricated to reduce or eliminate damage to the LED layer.

FIELD OF THE DISCLOSURE

This relates generally to touch sensing, and more specifically tointegrating touch circuitry into a Light-Emitting Diode (LED) pixelstackup.

BACKGROUND OF THE DISCLOSURE

Many types of input devices are presently available for performingoperations in a computing system, such as buttons or keys, mice,trackballs, joysticks, touch sensor panels, touch screens and the like.Touch screens, in particular, are becoming increasingly popular becauseof their ease and versatility of operation as well as their decliningprice. Touch screens can include a touch sensor panel, which can be aclear panel with a touch-sensitive surface, and a display device such asa Light-Emitting Diode (LED) display (for example, an OrganicLight-Emitting Diode display (OLED) display) that can be positionedpartially or fully behind the panel so that the touch-sensitive surfacecan cover at least a portion of the viewable area of the display device.OLED displays are becoming more widespread with advances in OLEDtechnology.

Touch screens can allow a user to perform various functions by touchingthe touch sensor panel using a finger, stylus or other object at alocation often dictated by a user interface (UI) being displayed by thedisplay device. In general, touch screens can recognize a touch and theposition of the touch on the touch sensor panel, and the computingsystem can then interpret the touch in accordance with the displayappearing at the time of the touch, and thereafter can perform one ormore actions based on the touch. In the case of some touch sensingsystems, a physical touch on the display is not needed to detect atouch. For example, in some capacitive-type touch sensing systems,fringing fields used to detect touch can extend beyond the surface ofthe display, and objects approaching the surface may be detected nearthe surface without actually touching the surface.

Capacitive touch sensor panels can be formed from a matrix of drive andsense lines of a substantially transparent conductive material, such asIndium Tin Oxide (ITO), often arranged in rows and columns in horizontaland vertical directions on a substantially transparent substrate. It isdue in part to their substantial transparency that capacitive touchsensor panels can be overlaid on LED or OLED displays to form a touchscreen (on-cell touch), as described above. However, integrating touchcircuitry into an LED or OLED display pixel stackup (i.e., the stackedmaterial layers forming the LED or OLED display pixels) can be desired(in-cell touch).

SUMMARY OF THE DISCLOSURE

The following description includes examples of integrating touchcircuitry into an LED display pixel stackup of a touch screen device.The touch screen can include a transistor layer, an LED layer and afirst layer that can be configured to operate as an LED cathode during adisplay phase and as touch circuitry during a touch sensing phase. Thetransistor layer can be at least partially utilized for transitioningbetween the display phase and the touch sensing phase. Furthermore, thetouch screen can be fabricated in such a way as to reduce or eliminatedamage to the LED layer during fabrication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an example mobile telephone that includes a touchscreen.

FIG. 1B illustrates an example digital media player that includes atouch screen.

FIG. 1C illustrates an example personal computer that includes a touchscreen.

FIG. 2 is a block diagram of an example computing system thatillustrates one implementation of an example touch screen according toexamples of the disclosure.

FIG. 3A is a more detailed view of a touch screen showing an exampleconfiguration of drive lines and sense lines according to examples ofthe disclosure.

FIG. 3B is a more detailed view of a touch screen showing anotherexample configuration of drive lines and sense lines according toexamples of the disclosure.

FIG. 4 illustrates an example configuration in which common electrodescan form portions of the touch sensing circuitry of a touch sensingsystem.

FIG. 5 is a three-dimensional illustration of an exploded view (expandedin the z-direction) of example display pixel stackups showing some ofthe elements within the pixel stackups of an example integrated touchscreen.

FIG. 6 shows partial circuit diagrams of some of the touch sensingcircuitry within display pixels in a drive region segment and a senseregion of an example touch screen according to examples of thedisclosure.

FIG. 7A illustrates an exemplary AMOLED pixel circuit that can be usedin a regular top emission OLED display.

FIG. 7B illustrates another exemplary AMOLED pixel circuit that can beused in a regular top emission OLED display.

FIG. 7C illustrates an exemplary AMOLED pixel circuit that can be usedin an inverted OLED display.

FIGS. 8A and 8B illustrate an exemplary AMOLED pixel circuitconfiguration and operation for turning on and off an OLED elementduring touch sensing and display phases of the touch screen of thedisclosure.

FIGS. 9A-9D illustrate further exemplary AMOLED pixel circuitconfigurations and operations for turning on and off an OLED elementduring touch sensing and display phases of the touch screen of thisdisclosure.

FIG. 10 illustrates an exemplary top emission OLED material stackaccording to examples of the disclosure.

FIGS. 11A and 11B-1 through 11B-5 illustrate an exemplary process forpatterning the cathode layer according to examples of the disclosure.

FIGS. 12A and 12B-1 through 12B-5 illustrate another exemplary processfor patterning the cathode layer according to examples of thedisclosure.

FIGS. 13A and 13B-1 through 13B-6 illustrate another exemplary processfor patterning the cathode layer according to examples of thedisclosure.

FIGS. 14A and 14B illustrate an exemplary way of lowering the sheetresistance of the cathode layer according to examples of the disclosure.

FIGS. 15A and 15B-1 through 15B-6 illustrate an exemplary process forforming a drive line connection over OLED layers according to examplesof the disclosure.

FIGS. 16A-1 through 16A-3 and 16B-1 through 16B-3 illustrate anexemplary process for performing shadow mask deposition of the cathodelayer according to examples of this disclosure.

FIGS. 17A-1 through 17A-2 and 17B-1 through 17B-3 illustrate anexemplary process for performing laser ablation to form drive and sensesegments according to examples of the disclosure.

FIGS. 18A through 18C and 18D-1 through 18D-3 illustrate an exemplaryprocess for modifying the distance between adjacent OLED emission layersaccording to examples of the disclosure.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples that can be practiced. It is tobe understood that other examples can be used and structural changes canbe made without departing from the scope of the disclosed examples.

Many types of input devices are presently available for performingoperations in a computing system. Touch screens, in particular, arebecoming increasingly popular because of their ease and versatility ofoperation as well as their declining price. Touch screens can include atouch sensor panel, which can be a clear panel with a touch-sensitivesurface, and a display device such as a Light-Emitting Diode (LED)display (for example, an Organic Light-Emitting Diode display (OLED)display) that can be positioned partially or fully behind the panel sothat the touch-sensitive surface can cover at least a portion of theviewable area of the display device. OLED displays are becoming morewidespread with advances in OLED technology.

Touch screens can allow a user to perform various functions by touchingthe touch sensor panel using a finger, stylus or other object at alocation often dictated by a user interface (UI) being displayed by thedisplay device. In general, touch screens can recognize a touch and theposition of the touch on the touch sensor panel, and the computingsystem can then interpret the touch in accordance with the displayappearing at the time of the touch, and thereafter can perform one ormore actions based on the touch. In the case of some touch sensingsystems, a physical touch on the display is not needed to detect atouch. For example, in some capacitive-type touch sensing systems,fringing fields used to detect touch can extend beyond the surface ofthe display, and objects approaching the surface may be detected nearthe surface without actually touching the surface.

Capacitive touch sensor panels can be formed from a matrix of drive andsense lines of a substantially transparent conductive material, such asIndium Tin Oxide (ITO), often arranged in rows and columns in horizontaland vertical directions on a substantially transparent substrate. It isdue in part to their substantial transparency that capacitive touchsensor panels can be overlaid on LED or OLED displays to form a touchscreen (on-cell touch), as described above. However, integrating touchcircuitry into an LED or OLED display pixel stackup (i.e., the stackedmaterial layers forming the LED or OLED display pixels) can be desired(in-cell touch).

FIGS. 1A-1C show example systems in which a touch screen according toexamples of the disclosure may be implemented. FIG. 1A illustrates anexample mobile telephone 136 that includes a touch screen 124. FIG. 1Billustrates an example digital media player 140 that includes a touchscreen 126. FIG. 1C illustrates an example personal computer 144 thatincludes a touch screen 128. Although not shown in the figures, thepersonal computer 144 can also be a tablet computer or a desktopcomputer with a touch-sensitive display. Touch screens 124, 126, and 128may be based on, for example, self capacitance or mutual capacitance, oranother touch sensing technology. For example, in a self capacitancebased touch system, an individual electrode with a self-capacitance toground can be used to form a touch pixel (touch node) for detectingtouch. As an object approaches the touch pixel, an additionalcapacitance to ground can be formed between the object and the touchpixel. The additional capacitance to ground can result in a net increasein the self-capacitance seen by the touch pixel. This increase inself-capacitance can be detected and measured by a touch sensing systemto determine the positions of multiple objects when they touch the touchscreen. A mutual capacitance based touch system can include, forexample, drive regions and sense regions, such as drive lines and senselines. For example, drive lines can be formed in rows while sense linescan be formed in columns (e.g., orthogonal). Touch pixels (touch nodes)can be formed at the intersections or adjacencies (in single layerconfigurations) of the rows and columns. During operation, the rows canbe stimulated with an AC waveform and a mutual capacitance can be formedbetween the row and the column of the touch pixel. As an objectapproaches the touch pixel, some of the charge being coupled between therow and column of the touch pixel can instead be coupled onto theobject. This reduction in charge coupling across the touch pixel canresult in a net decrease in the mutual capacitance between the row andthe column and a reduction in the AC waveform being coupled across thetouch pixel. This reduction in the charge-coupled AC waveform can bedetected and measured by the touch sensing system to determine thepositions of multiple objects when they touch the touch screen. In someexamples, a touch screen can be multi-touch, single touch, projectionscan, full-imaging multi-touch, or any capacitive touch.

FIG. 2 is a block diagram of an example computing system 200 thatillustrates one implementation of an example touch screen 220 accordingto examples of the disclosure. Computing system 200 could be includedin, for example, mobile telephone 136, digital media player 140,personal computer 144, or any mobile or non-mobile computing device thatincludes a touch screen. Computing system 200 can include a touchsensing system including one or more touch processors 202, peripherals204, a touch controller 206, and touch sensing circuitry (described inmore detail below). Peripherals 204 can include, but are not limited to,random access memory (RAM) or other types of memory or storage, watchdogtimers and the like. Touch controller 206 can include, but is notlimited to, one or more sense channels 208, channel scan logic 210 anddriver logic 214. Channel scan logic 210 can access RAM 212,autonomously read data from the sense channels and provide control forthe sense channels. In addition, channel scan logic 210 can controldriver logic 214 to generate stimulation signals 216 at variousfrequencies and/or phases that can be selectively applied to driveregions of the touch sensing circuitry of touch screen 220, as describedin more detail below. In some examples, touch controller 206, touchprocessor 202 and peripherals 204 can be integrated into a singleapplication specific integrated circuit (ASIC).

Computing system 200 can also include a host processor 228 for receivingoutputs from touch processor 202 and performing actions based on theoutputs. For example, host processor 228 can be connected to programstorage 232 and a display controller, such as an Active-Matrix OrganicLight-Emitting Diode (AMOLED) driver 234. It is understood that althoughthe examples of the disclosure are described with reference to AMOLEDdisplays, the scope of the disclosure is not so limited and can extendto other types of LED displays such as Passive-Matrix OrganicLight-Emitting Diode (PMOLED) displays.

Host processor 228 can use AMOLED driver 234 to generate an image ontouch screen 220, such as an image of a user interface (UI), and can usetouch processor 202 and touch controller 206 to detect a touch on ornear touch screen 220, such as a touch input to the displayed UI. Thetouch input can be used by computer programs stored in program storage232 to perform actions that can include, but are not limited to, movingan object such as a cursor or pointer, scrolling or panning, adjustingcontrol settings, opening a file or document, viewing a menu, making aselection, executing instructions, operating a peripheral deviceconnected to the host device, answering a telephone call, placing atelephone call, terminating a telephone call, changing the volume oraudio settings, storing information related to telephone communicationssuch as addresses, frequently dialed numbers, received calls, missedcalls, logging onto a computer or a computer network, permittingauthorized individuals access to restricted areas of the computer orcomputer network, loading a user profile associated with a user'spreferred arrangement of the computer desktop, permitting access to webcontent, launching a particular program, encrypting or decoding amessage, and/or the like. Host processor 228 can also perform additionalfunctions that may not be related to touch processing.

Touch screen 220 can include touch sensing circuitry that can include acapacitive sensing medium having a plurality of drive lines 222 and aplurality of sense lines 223. It should be noted that the term “lines”is sometimes used herein to mean simply conductive pathways, as oneskilled in the art will readily understand, and is not limited toelements that are strictly linear, but includes pathways that changedirection, and includes pathways of different size, shape, materials,etc. Drive lines 222 can be driven by stimulation signals 216 fromdriver logic 214 through a drive interface 224, and resulting sensesignals 217 generated in sense lines 223 can be transmitted through asense interface 225 to sense channels 208 (also referred to as an eventdetection and demodulation circuit) in touch controller 206. In thisway, drive lines and sense lines can be part of the touch sensingcircuitry that can interact to form capacitive sensing nodes, which canbe thought of as touch picture elements (touch pixels), such as touchpixels 226 and 227. This way of understanding can be particularly usefulwhen touch screen 220 is viewed as capturing an “image” of touch. Inother words, after touch controller 206 has determined whether a touchhas been detected at each touch pixel in the touch screen, the patternof touch pixels in the touch screen at which a touch occurred can bethought of as an “image” of touch (e.g., a pattern of fingers touchingthe touch screen).

In some examples, touch screen 220 can be an integrated touch screen inwhich touch sensing circuit elements of the touch sensing system can beintegrated into the display pixel stackups of a display. An exampleintegrated touch screen in which examples of the disclosure can beimplemented will now be described with reference to FIGS. 3-6. FIG. 3Ais a more detailed view of touch screen 220 showing an exampleconfiguration of drive lines 222 and sense lines 223 according toexamples of the disclosure. As shown in FIG. 3A, each drive line 222 canbe formed of one or more drive line segments 301 that can beelectrically connected by drive line links 303 at connections 305. Driveline links 303 are not electrically connected to sense lines 223,rather, the drive line links can bypass the sense lines through bypasses307. Drive lines 222 and sense lines 223 can interact capacitively toform touch pixels such as touch pixels 226 and 227. Drive lines 222(i.e., drive line segments 301 and corresponding drive line links 303)and sense lines 223 can be formed of electrical circuit elements intouch screen 220. In the example configuration of FIG. 3A, each of touchpixels 226 and 227 can include a portion of one drive line segment 301,a portion of a sense line 223, and a portion of another drive linesegment. For example, touch pixel 226 can include a right-half portion309 of a drive line segment 301 on one side of a portion 311 of a senseline 223, and a left-half portion 313 of a drive line segment on theopposite side of portion 311 of the sense line.

FIG. 3B is a more detailed view of touch screen 220 showing anotherexample configuration of drive lines 222 and sense lines 223 accordingto examples of the disclosure. As shown in FIG. 3B, each sense line 223can be formed of one or more sense line segments 313 that can beelectrically connected by sense line links 315 at connections 317. Senseline links 315 are not electrically connected to drive lines 222,rather, the sense line links can bypass the drive lines through bypasses319. Drive lines 222 and sense lines 223 can interact capacitively toform touch pixels such as touch pixels 226 and 227. Drive lines 222 andsense lines 223 (i.e., sense line segments 315 and corresponding senseline links 315) can be formed of electrical circuit elements in touchscreen 220. In the example of FIG. 3B, each of touch pixels 226 and 227can include a portion of a drive line 222 and a sense line segment 313.For example, touch pixel 226 can include a portion 321 of a drive line222 and sense line segment 323. For ease of description, the examples ofthe disclosure will be described using the example configuration of FIG.3A, although it is understood that the examples of the disclosure arenot limited to such a configuration.

The circuit elements in touch screen 220 can include, for example,elements that can exist in AMOLED displays, as described above. It isnoted that circuit elements are not limited to whole circuit components,such as a whole capacitor, a whole transistor, etc., but can includeportions of circuitry, such as only one of the two plates of a parallelplate capacitor. FIG. 4 illustrates an example configuration in whichcommon electrodes 401 can form portions of the touch sensing circuitryof a touch sensing system. Each display pixel 407 can include a portionof a common electrode 401, which is a circuit element of the displaysystem circuitry in the pixel stackup (i.e., the stacked material layersforming the display pixels) of the display pixels of some types ofAMOLED displays that can operate as part of the display system todisplay an image.

In the example shown in FIG. 4, each common electrode 401 can serve as amulti-function circuit element that can operate as display circuitry ofthe display system of touch screen 220 and can also operate as touchsensing circuitry of the touch sensing system. In this example, eachcommon electrode 401 can operate as a common electrode of the displaycircuitry of the touch screen 220, and can also operate together whengrouped with other common electrodes as touch sensing circuitry of thetouch screen. For example, a common electrode 401 can operate as acapacitive part of a drive line (i.e., a drive line segment 403) or as acapacitive sense line 405 of the touch sensing circuitry during thetouch sensing phase. Other circuit elements of touch screen 220 can formpart of the touch sensing circuitry by, for example, switchingelectrical connections, etc. In general, each of the touch sensingcircuit elements may be either a multi-function circuit element that canform part of the touch sensing circuitry and can perform one or moreother functions, such as forming part of the display circuitry, or maybe a single-function circuit element that can operate as touch sensingcircuitry only. Similarly, each of the display circuit elements may beeither a multi-function circuit element that can operate as displaycircuitry and perform one or more other functions, such as operating astouch sensing circuitry, or may be a single-function circuit elementthat can operate as display circuitry only. Therefore, in some examples,some of the circuit elements in the display pixel stackups can bemulti-function circuit elements and other circuit elements may besingle-function circuit elements. In other examples, all of the circuitelements of the display pixel stackups may be single-function circuitelements.

In addition, although examples herein may describe the display circuitryas operating during a display phase, and describe the touch sensingcircuitry as operating during a touch sensing phase, it should beunderstood that a display phase and a touch sensing phase may beoperated at the same time, e.g., partially or completely overlap, or thedisplay phase and touch sensing phase may operate at different times.Also, although examples herein describe certain circuit elements asbeing multi-function and other circuit elements as beingsingle-function, it should be understood that the circuit elements arenot limited to the particular functionality in other examples. In otherwords, a circuit element that is described in one example herein as asingle-function circuit element may be configured as a multi-functioncircuit element in other examples, and vice versa.

Multi-function circuit elements of display pixels of the touch screencan operate in both the display phase and the touch sensing phase. Forexample, during a touch sensing phase, common electrodes 401 can formtouch signal lines, such as drive regions and sense regions. In someexamples circuit elements can be grouped to form a continuous touchsignal line of one type and a segmented touch signal line of anothertype. For example, FIG. 4 shows one example in which drive line segments403 and sense lines 405 correspond to drive line segments 301 and senselines 223 of touch screen 220. Other configurations are possible inother examples; for example, common electrodes 401 could be providedsuch that drive lines are each formed of a continuous drive region andsense lines are each formed of a plurality of sense region segmentslinked together through connections that bypass a drive region, asillustrated in the example of FIG. 3B.

The drive regions in the examples of FIGS. 3A and 4 are shown asrectangular regions including a plurality of display pixels, and thesense regions of FIGS. 3A, 3B, and 4 are shown as rectangular regionsincluding a plurality of display pixels extending the vertical length ofthe AMOLED display. In some examples, a touch pixel of the configurationof FIG. 4 can include, for example, a 64×64 area of display pixels.However, the drive and sense regions are not limited to the shapes,orientations, and positions shown, but can include any suitableconfigurations according to examples of the disclosure. It is to beunderstood that the display pixels included in the touch pixels are notlimited to those described above, but can be any suitable size or shapeto permit touch capabilities according to examples of the disclosure.

FIG. 5 is a three-dimensional illustration of an exploded view (expandedin the z-direction) of example display pixel stackups 500 showing someof the elements within the pixel stackups of an example integrated touchscreen 550. Stackups 500 can include a configuration of conductive linesthat can be used to link drive region segments to form drive lines.

Stackups 500 can include elements in a first metal (M1) layer 501, asecond metal (M2) layer 503, and a common electrode layer 505. Eachdisplay pixel can include a portion of a common electrode 509, such ascommon electrodes 401 in FIG. 4, that is formed in common electrodelayer 505. In some display pixels, breaks 513 can be included in thecommon electrodes 509 to separate different segments of commonelectrodes to form drive region segments 515 and a sense region 517,such as drive line segments 403 and sense line 405, respectively. Breaks513 can include breaks in the x-direction that can separate drive regionsegments 515 from sense region 517, and breaks in the y-direction thatcan separate one drive region segment 515 from another drive regionsegment. M1 layer 501 can include tunnel lines 519 that can electricallyconnect together drive region segments 515 through connections, such asconductive vias 521, which can electrically connect tunnel line 519 tothe common electrode in drive region segment display pixels. Tunnel line519 can run through the display pixels in sense region 517 with noconnections to the common electrode 509 in the sense region, i.e., novias 521 in the sense region. The M1 layer can also include gate lines520. M2 layer 503 can include data lines 523. Only one gate line 520 andone data line 523 are shown for the sake of clarity; however, a touchscreen can include a gate line running through each horizontal row ofdisplay pixels and multiple data lines running through each vertical rowof display pixels, for example, one data line for each red, green, blue(RGB) color sub-pixel in each pixel in a vertical row of an RGB AMOLEDdisplay integrated touch screen. Although M1 layer 501 is shown to bebelow M2 layer 503, which is shown to be below common electrode layer505, it is understood that the ordering of these layers in thez-direction, as well as the ordering of the elements in each of theselayers, can differ from what is shown in FIG. 5. For example, theelements in M1 layer 501 (e.g., tunnel line 519 and gate line 520) canbe in M2 layer instead, or can be distributed amongst different metallayers.

Structures such as tunnel lines 519 and conductive vias 521 can operateas a touch sensing circuitry of a touch sensing system to detect touchduring a touch sensing phase of the touch screen 550. Structures such asdata lines 523, along with other pixel stackup elements such astransistors, pixel electrodes, common voltage lines, data lines, etc.(not shown), can operate as display circuitry of a display system todisplay an image on the touch screen 550 during a display phase.Structures such as common electrodes 509 can operate as multifunctioncircuit elements that can operate as part of both the touch sensingsystem and the display system.

For example, in operation during a touch sensing phase, gate lines 520can be held to a fixed voltage while stimulation signals can betransmitted through a row of drive region segments 515 connected bytunnel lines 519 and conductive vias 521 to form electric fields betweenthe stimulated drive region segments and sense region 517 to createtouch pixels, such as touch pixel 226 in FIG. 2. In this way, the row ofconnected-together drive region segments 515 can operate as a driveline, such as drive line 222, and sense region 517 can operate as asense line, such as sense line 223. When an object such as a fingerapproaches or touches a touch pixel, the object can affect the electricfields extending between the drive region segments 515 and the senseregion 517, thereby reducing the amount of charge capacitively coupledto the sense region. This reduction in charge can be sensed by a sensechannel of a touch sensing controller connected to the touch screen 550,such as touch controller 206 shown in FIG. 2, and stored in a memoryalong with similar information of other touch pixels to create an“image” of touch.

A touch sensing operation according to examples of the disclosure willbe described with reference to FIG. 6. FIG. 6 shows partial circuitdiagrams of some of the touch sensing circuitry within display pixels ina drive region segment 601 and a sense region 603 of an example touchscreen according to examples of the disclosure. For the sake of clarity,only one drive region segment is shown. Also for the sake of clarity,FIG. 6 includes circuit elements illustrated with dashed lines tosignify some circuit elements operate primarily as part of the displaycircuitry and not the touch sensing circuitry. In addition, a touchsensing operation is described primarily in terms of a single displaypixel 601 a of drive region segment 601 and a single display pixel 603 aof sense region 603. However, it is understood that other display pixelsin drive region segment 601 can include the same touch sensing circuitryas described below for display pixel 601 a, and the other display pixelsin sense region 603 can include the same touch sensing circuitry asdescribed below for display pixel 603 a. Thus, the description of theoperation of display pixel 601 a and display pixel 603 a can beconsidered as a description of the operation of drive region segment 601and sense region 603, respectively.

Referring to FIG. 6, drive region segment 601 can include a plurality ofdisplay pixels including display pixel 601 a. Display pixel 601 a caninclude a transistor such as thin film transistor (TFT) 607, a data line611, a V_(DD) line 613, an LED element such as OLED element 615, and aportion 619 of common electrode 617. Sense region 603 can include aplurality of display pixels including display pixel 603 a. Display pixel603 a can include a transistor such as TFT 609, a data line 612, an LEDelement such as OLED element 616, and a portion 620 of common electrode618. TFT 609 can be connected to the same V_(DD) line 613 as TFT 607.

During a touch sensing phase, OLED elements 615 and 616 can bemaintained in an off state, the specifics of which will be describedlater. Drive signals can be applied to common electrode 617 through atunnel line 621. The drive signals can generate an electric field 623between common electrode 617 of drive region segment 601 and commonelectrode 618 of sense region 603, which can be connected to a senseamplifier, such as a charge amplifier 626. Electrical charge can beinjected into common electrode 618 of sense region 603, and chargeamplifier 626 can convert the injected charge into a voltage that can bemeasured. The amount of charge injected, and consequently the measuredvoltage, can depend on the proximity of a touch object, such as a finger627, to the drive 601 and sense 603 regions. In this way, the measuredvoltage can provide an indication of touch on or near the touch screen.

The operation of part of the display circuitry of the AMOLED touchscreen during a display phase according to examples of the disclosurewill be described with reference to FIGS. 7A-7C. FIG. 7A illustrates anexemplary AMOLED pixel circuit 750 that can be used in a regular topemission OLED display. The specifics of top emission and bottom emissionOLEDs will be described later. The pixel circuit 750 can include an OLEDelement 701 having two terminals (a cathode 703 terminal and an anode709 terminal), a p-type transistor such as TFT T2 705, and an n-typetransistor such as TFT T1 707. The cathode 703 terminal of OLED element701 can be electrically connected to cathode. Cathode 703 can be thesignal line common to a plurality of pixel circuits in the touch screen,and can correspond to common electrode 401 or 509, for example. Theanode 709 terminal of OLED element 701 can be electrically connected toanode. OLED element 701 can be connected to cathode 703 and anode 709 insuch a way as to allow current to flow through OLED element when thevoltage at anode is higher than the voltage at cathode (i.e., OLEDelement is on, or “forward biased”). OLED element 701 can emit lightwhen it is on. When the voltage at anode 709 is lower than the voltageat cathode 703, substantially no current can flow through OLED element701 (i.e., OLED element is off, or “reverse biased”). OLED element 701can emit substantially no light when it is off.

Anode 709 can be electrically connected to the drain terminal of T2 705.The gate and source terminals of T2 705 can be capacitively coupled byway of capacitor C_(st) 711, where one terminal of C_(st) can beelectrically connected to the gate terminal of T2 and the other terminalof C_(st) can be electrically connected to the source terminal of T2.The source terminal of T2 705 can further be electrically connected toV_(DD) 713. The gate terminal of T2 705 can further be electricallyconnected to the drain terminal of T1 707. The gate terminal of T1 canbe electrically connected to gate line 715, and the source terminal ofT1 can be electrically connected to data line 717.

FIG. 7B illustrates another exemplary AMOLED pixel circuit 752 that canbe used in a regular top emission OLED display. In FIG. 7B, T2 719 canbe an n-type TFT instead of a p-type TFT as in FIG. 7A. Therefore, thesource terminal of T2 719 can be electrically connected to anode 709,and the drain terminal of T2 can be electrically connected to V_(DD)713. The gate and source terminals of T2 719 can continue to becapacitively coupled by way of capacitor C_(st) 711. The remainingelements of pixel circuit 752 can be the same as that of pixel circuit750 in FIG. 7A.

FIG. 7C illustrates an exemplary AMOLED pixel circuit 754 that can beused in an inverted OLED display. In the case of an inverted OLEDdisplay, the anode 709, and not the cathode 703, can be the commonelectrode, and the anode can be above the OLED element 701. Theconfiguration of T2 719, C_(st) 711, T1 707, and the other circuitelements can be the same as that in FIG. 7B. However, the cathode 703terminal of OLED element 701 can be electrically connected to the drainterminal of T2 719, and the anode 709 terminal of OLED element can beelectrically connected to V_(DD) 713.

Referring to FIG. 7A, during a display phase of the touch screenaccording to the examples of the disclosure, OLED element 701 can beforward biased (and can thus have current flowing through it), and canbe emitting light. To allow for current to flow through OLED element701, the voltage at gate line 715 can be sufficiently high to turn on T1707 (i.e., the gate to source voltage of T1 can be sufficiently high toturn on T1). When T1 707 is on, T1 can act substantially as ashort-circuit and can cause the voltage at data line 717 to besubstantially mirrored at the gate terminal of T2 705. The voltage atdata line 717, and thus the voltage at the gate terminal of T2 705, canbe sufficiently low to turn on T2 705 (i.e., the gate to source voltageof T2 can be sufficiently low to turn on T2). When T2 705 is on, T2 canact substantially as a short-circuit and can cause the voltage at V_(DD)713 to be substantially mirrored at anode 709. For OLED element 701 tobe forward biased, the voltage at anode 709, and thus the voltage atV_(DD) 713, can be higher than the voltage at cathode 703. When thisoccurs, OLED element 701 can be forward biased, can have current flowingthrough it, and can be emitting light. Although this description hasbeen provided with respect to the circuit of FIG. 7A, it is understoodthat the operation of the circuits of FIGS. 7B and 7C is substantiallysimilar to the operation of the circuit of FIG. 7A. Further, for thesake of clarity, the examples below will be provided with respect to thestructure of the circuit of FIG. 7A; however, it is understood that theexamples may be adapted to be used with the circuits of FIGS. 7B and 7C.For example, whereas the voltage at the gate terminal of a p-type TFTcan be sufficiently low to turn on the p-type TFT, the opposite can betrue for an n-type TFT; that is, the voltage at the gate terminal of ann-type TFT can be sufficiently high to turn on the n-type TFT. Thismodification can be extended to the circuits of FIGS. 7B and 7C to allowfor proper operation.

To facilitate the operation of the AMOLED touch screen according toexamples of the disclosure, portions of the display circuitry of thetouch screen can be turned off during a touch sensing phase of the touchscreen, and can be turned on during a display phase of the touch screen.Exemplary turn-off operations will be described with reference to FIGS.8 and 9A-9C. Although FIGS. 8 and 9A-9C are provided with displaycircuits that utilize a p-type TFT, as shown in FIG. 7A, it isunderstood that the circuits of FIGS. 7B and 7C can be similarlyutilized in the structures of FIGS. 8 and 9A-9C.

FIGS. 8A and 8B illustrate an exemplary AMOLED pixel circuit 850configuration and operation for turning on and off an OLED elementduring touch sensing and display phases of the touch screen of thedisclosure. The circuit configuration of FIGS. 8A and 8B is that of FIG.7A, and a partial circuit diagram of the circuit of FIG. 7A is providedin FIG. 8B. FIG. 8A illustrates the voltage at V_(DD) 801 during atransition from a pixel circuit ON phase to a pixel circuit OFF phase.During the pixel circuit ON phase, the voltage at V_(DD) 801 can beV_(ON). V_(ON) can be sufficiently high, as described with reference toFIG. 7A, such that OLED element 803 can be forward biased. All of theother voltages of the circuit can be set such that the circuit operatesas described with reference to FIG. 7A.

To transition to a touch sensing phase in which OLED element 803 can beoff, the voltage at gate line 711 (not shown in FIG. 8B) of FIG. 7A canbe sufficiently low to turn off T1 707 (not shown in FIG. 8B). This canresult in the voltage at the gate terminal of T2 805 to be floating.Because the gate terminal of T2 805 can be capacitively coupled to thesource terminal of T2 by way of C_(st) 807, the difference between thegate and source voltages of T2 can remain substantially constant as longas the gate of T2 is floating (i.e., C_(st) can substantially maintainthe gate to source voltage of T2). Therefore, T2 805 can remain onirrespective of the voltage at V_(DD) 801.

Because T2 805 can remain on irrespective of the voltage at V_(DD) 801,the voltage at V_(DD) can be lowered from V_(ON) to V_(OFF) whilemaintaining T2 in an on state. Because T2 805 can remain on, it canbehave substantially like a short-circuit, and therefore the voltage atV_(DD) 801 can be substantially mirrored at anode 809. If V_(OFF) isless than the voltage at cathode 811, OLED element 803 can be reversebiased, as described previously. As such, OLED element 803 can be off,and can emit substantially no light, thus turning off pixel circuit 850.

During a touch sensing phase, when pixel circuit 850 is off, cathode 811can be utilized as part of the touch sensing circuitry (i.e., as part ofcommon electrode 617), as described with reference to FIG. 6. Thevoltage at V_(DD) 801 during the touch sensing phase (V_(OFF)) can besufficiently low such that through the range of voltages that can existat cathode 811 during the touch sensing phase, OLED element 803 canremain reverse biased, and thus off. For example, if the voltage atcathode 811 during the touch sensing phase can vary from −5V to +5V,V_(OFF) can be less than −5V to ensure that OLED element 803 can remainreverse biased. To transition from an off state back to an on state, thesteps described above can be reversed such that display phase operationcan resume.

FIGS. 9A-9D illustrate further exemplary AMOLED pixel circuitconfigurations and operations for turning on and off an OLED elementduring touch sensing and display phases of the touch screen of thisdisclosure. The AMOLED pixel circuit 950 of FIG. 9B is that of FIG. 7A,except that an additional p-type TFT T_(EM1) 915 can be electricallyconnected in series with T2 905 and OLED element 903, positioned betweenT2 and OLED element. During a display phase of the touch screen, thevoltage at the gate terminal of T_(EM1) 915 (V_(G-EM) 913) can besufficiently low such that T_(EM1) can be on. When on, T_(EM1) 915 canact substantially as a short-circuit and may not substantially affectthe current flowing through OLED element 903. The remaining elements ofthe pixel circuit 950 can operate as described with reference to FIG.7A. Turning OLED element 903 off (i.e., stopping current flow throughOLED element) during a touch sensing phase of the touch screen can beaccomplished by setting the voltage at V_(G-EM) 913 to be sufficientlyhigh such that T_(EM1) 915 can be off. When off, T_(EM1) 915 can actsubstantially as an open-circuit, thus substantially preventing currentflow through OLED element 903. This, in turn, can result in OLED element903 turning off. In this way, the voltage at V_(DD) 901 need not beregulated as described with reference to FIG. 8 to turn off the pixelcircuit 950. FIG. 9A illustrates the voltage at V_(G-EM) 913 during adisplay phase and a touch sensing phase of the touch screen.

FIGS. 9C and 9D illustrate alternative configurations of the pixelcircuit of FIG. 9B, but can operate in substantially the same manner. InFIG. 9C, T_(EM1) 915 can be positioned between V_(DD) 901 and T2 905,instead of between T2 and OLED element 903; however, the pixel circuit952 of FIG. 9C can otherwise operate in the same manner as the circuitof FIG. 9B. FIG. 9D illustrates a pixel circuit 954 that has two p-typeTFTs electrically connected in series with T2 905: T_(EM1) 915 andT_(EM2) 916. T_(EM1) 915 can be positioned between T2 905 and OLEDelement 903, and T_(EM2) 916 can be positioned between T2 and V_(DD)901. During a touch sensing phase of the touch screen, T_(EM1) 915 andT_(EM2) 916 can be turned off in the manner described above withreference to FIG. 9B. During a display phase of the touch screen,T_(EM1) 915 and T_(EM2) 916 can be turned on in the manner describedabove with reference to FIG. 9B.

Although T_(EM1) 915 and T_(EM2) 916 have been described as being p-typetransistors such as TFTs, it is understood that either or both caninstead be n-type TFTs, in which case the voltages required to turn themon and off would be the reverse of what was described above. That is tosay, if T_(EM1) 915 were an n-type TFT, the voltage needed at V_(G-EM)913 to turn on T_(EM1) would be high, and the voltage needed at V_(G-EM)to turn off T_(EM1) would be low. The appropriate changes to theoperation described above can be made to allow for the proper operationof the pixel circuits described.

The examples of this disclosure can be implemented in many types of LEDdisplays, including both top emission OLED displays and bottom emissionOLED displays. In bottom emission OLED displays, the transistors such asTFTs, metal routing, capacitors and OLED layers can share area on thesubstrate glass. Because the OLED layers can share space with the TFTs,the metal routing, and the capacitors, the remaining area for use by theOLED layers can be limited. This can result in small-area OLED layers,which can require high driving current densities to generate sufficientOLED light emission. In top emission OLED displays, the OLED layers canbe formed on top of the TFT layers, which can provide the OLED layerswith fewer area restrictions as compared with bottom emission OLEDdisplays. Thus, lower driving current densities can be required togenerate sufficient OLED light emission.

FIG. 10 illustrates an exemplary top emission OLED material stack 1050according to examples of the disclosure. TFT layer 1001 can includevarious circuit elements of the pixel circuits of FIG. 7, 8 or 9,including T2 905, T_(EM1) 915 or T_(EM2) 916. PLN 1003 can be aplanarization layer for electrically isolating the circuit elements ofTFT layer 1001 from the layers above, and for providing a substantiallyflat layer for facilitating the fabrication of the layers above it.Anode 1007 can provide an electrical connection between the circuitelements of TFT layer 1001 and OLED layer 1009. Anode 1007 cancorrespond to anode 709, 809, and/or 909. OLED layer 1009 can correspondto OLED element 616, 701, 803 and/or 903. PDL 1005 can be a layer forelectrically isolating adjacent anodes 1007 and OLED layers 1009.Finally, cathode 1011 can provide an electrical connection to OLEDlayers 1009, and can correspond to cathode 703, 811 and/or 911, forexample. Anode 1007 and cathode 1011 can be formed of conductivematerials; for example, cathode can be formed of many different types oftransparent conductive materials, such as Indium Tin Oxide (ITO) orIndium Zinc Oxide (IZO). During a display phase of the touch screen,when current is flowing from TFT layer 1001, through anode 1007 and OLEDlayer 1009, to cathode 1011, OLED layer can be on, and can emit lightthrough cathode to display an image on the touch screen.

To facilitate the operation of the examples of this disclosure, it canbe desired that the cathode 1011 of FIG. 10 be patterned such that,during a touch sensing phase, cathode can operate as distinct drive andsense segments, and during a display phase, cathode can operate as acommon electrode for the pixel circuits of the touch screen. Therefore,it can be necessary to electrically isolate portions of cathode 1011 toform segments such as drive line segment 301 and sense line 223 as shownin FIG. 3A, while also providing for electrical connections, such asdrive links 303, between adjacent drive line segments to form drivelines 222. However, OLED layer 1009 underneath cathode 1011 can besensitive to processing steps taken subsequent to the forming ofcathode, which can make it difficult to pattern cathode as describedabove. FIGS. 11-17 illustrate various ways to provide the structure ofthe above-described cathode.

Unless otherwise noted, the opening of vias or the removal of materialin the exemplary processes of the disclosure can be accomplished by acombination of photolithography and etching. Photolithography can beused to define the desired etch pattern on the surface of the materialto be patterned, and the etching of the material in accordance with thedesired etch pattern can remove the desired portions of the material.The etching of the material can be performed by utilizing anyappropriate etch process, including but not limited to dry etching orwet etching. Further, unless otherwise noted, the deposition orformation of material can be accomplished by any appropriate depositionprocess, including but not limited to physical vapor deposition (PVD),chemical vapor deposition (CVD), electrochemical deposition (ECD),molecular beam epitaxy (MBE), or atomic layer deposition (ALD).

FIGS. 11A and 11B illustrate an exemplary process for patterning thecathode layer according to examples of the disclosure. FIG. 11A shows atop-view of a patterned cathode structure 1150 in accordance withexamples of the disclosure. Drive line segments 1101 can be on eitherside of sense line 1103, and can be electrically isolated from senseline by isolation slits 1110. Both drive line segments 1101 and senseline 1103 can be formed of cathode 1011 of FIG. 10. OLED layers 1105 canbe underneath drive line segments 1101 and sense line 1103, and cancorrespond to OLED layers 1009 of FIG. 10. Drive line segments 1101 canbe electrically connected to each other by way of anode connection 1107.Anode connection 1107 can be formed of anode 1007 of FIG. 10, and can bepositioned in between adjacent OLED layers 1105 so as to not overlap anyOLED layers. Anode connection 1107 can be electrically connected todrive line segments 1101 by way of vias 1109. The process steps forfabricating the patterned cathode structure 1150 of FIG. 11A will bedescribed with reference to FIG. 11B, which illustrates across-sectional view of cross-section X-Y at each process step.

FIG. 11B-1 illustrates the first step of the example process. Anodeconnection 1107 can be formed on PLN 1111. Anode connection 1107 can beformed at the same time, and of the same material, as anode 1007 of FIG.10, but can be electrically isolated from anode 1007 and can be in adifferent area of the touch screen (namely, not overlapping OLED layers1105). Organic passivation 1113 can be formed on anode connection 1107,and vias 1109 can be opened to allow for connection to anode connection1107. OLED layers 1105 can be formed in other areas of the touch screen(as shown in FIG. 11A, not shown in FIG. 11B). Finally, cathode 1115 canbe blanket deposited in vias 1109 and over organic passivation 1113.

FIG. 11B-2 illustrates the next step of the example process. A thin filmencapsulation layer TFE1 1117 can be formed on cathode 1115. Thin filmencapsulation layers like TFE1 1117, with good barrier properties, canprotect OLED layers 1105 that are below them from subsequent processsteps, such as photolithography and etching. Here, TFE1 1117 can protectOLED layers 1105 from the next steps in the process.

FIG. 11B-3 illustrates the next step of the example process. TFE1 1117can be etched to partially open isolation slits 1110. OLED layers 1105in other areas of the touch screen can be protected from the etching ofTFE1 1117 at isolation slits 1110 because of the coverage of TFE1 inthose areas.

FIG. 11B-4 illustrates the next step of the example process. Cathode1115 can be etched to complete the opening of isolation slits 1110. Withthe etching of cathode 1115 in this step, drive line segments 1101 andsense line 1103 can be defined, and drive line segments 1101 can beelectrically isolated from sense line 1103 because of the removal ofconductive cathode material between drive line segments and sense line.As described above, OLED layers 1105 in other areas of the touch screencan be protected from the etching of cathode 1115 at isolation slits1110 because the coverage of TFE1 1117 in those areas can protect OLEDlayers.

FIG. 11B-5 illustrates the final step of the example process. Thin filmencapsulation layer TFE2 1119 can be blanket deposited as a finalprotective layer over the material stack. As shown, drive line segments1101 can be electrically connected to each other through vias 1109 andanode connection 1107. Drive line segments 1101 can be electricallyisolated from sense line 1103 by isolation slits 1110. By way of theabove-described process, the fabrication of the drive and sense linestructure of FIG. 3A, over OLED layers, can be accomplished.

Although the steps of the above process have been presented in aparticular order, it is understood that the ordering of the processsteps can be modified, where appropriate. Such modification can also bedone for the processes presented in the remainder of the disclosure.

FIGS. 12A and 12B illustrate another exemplary process for patterningthe cathode layer according to examples of the disclosure. FIG. 12Ashows the same top-view of a patterned cathode structure 1250 as shownin FIG. 11A. The process steps of FIG. 12B can be the same as those ofFIG. 11B, except that in FIG. 12B-4, cathode 1215 can be oxidized,instead of etched, at isolation slits 1210. Oxidization of anelectrically conductive material such as cathode 1215 can reduce theconductivity of the material to substantially to that of an electricalinsulator. Therefore, oxidization of cathode 1215 at isolation slits1210 can electrically isolate adjacent portions of cathode, and can thusform drive line segments 1201 and sense line 1203. In all otherrespects, the process of FIG. 12 can be the same as the process of FIG.11.

FIGS. 13A and 13B illustrate another exemplary process for patterningthe cathode layer according to examples of the disclosure. Instead ofelectrically connecting adjacent drive line segments 1301 by way of anelectrical connection formed underneath the cathode 1315 of the touchscreen, adjacent drive line segments can be electrically connected byway of an electrical connection formed over the cathode of the touchscreen. FIG. 13A shows the same top-view of a patterned cathodestructure 1350 as shown in FIG. 11A. FIG. 13B shows the process stepsthat can be performed to form the patterned cathode structure 1350 ofFIG. 13A at cross-section X-Y.

FIG. 13B-1 illustrates the first step of the example process. Organicpassivation 1313 can be formed on PLN 1311. OLED layers 1305 can beformed in other areas of the touch screen (as shown in FIG. 13A, notshown in FIG. 13B). Finally, cathode 1315 can be blanket deposited tocover organic passivation 1313.

FIG. 13B-2 illustrates the next step of the example process. Thin filmencapsulation layer TFE1 1317 can be deposited over cathode 1315. TFE11317 can protect OLED layers 1305 from the next steps in the process.

FIG. 13B-3 illustrates the next step of the example process. TFE1 1317can be etched to partially open isolation slits 1310. OLED layers 1305in other areas of the touch screen can be protected from the etching ofTFE1 1317 because the coverage of TFE1 in those areas can protect OLEDlayers.

FIG. 13B-4 illustrates the next step of the example process. Cathode1315 can be etched to complete the opening of isolation slits 1310. Withthe etching of cathode 1315 in this step, drive line segments 1301 andsense line 1303 can be defined, and drive line segments can beelectrically isolated from the sense line because of the removal ofconductive cathode material between drive line segments and the senseline. As described above, OLED layers 1305 in other areas of the touchscreen can be protected from the etching of cathode 1315 because thecoverage of TFE1 1317 in those areas can protect OLED layers.

FIG. 13B-5 illustrates the next step of the example process. Thin filmencapsulation layer TFE2 1319 can be deposited, and vias 1309 can beetched in TFE1 1317 and TFE2 to allow for electrical connection tocathode 1315.

FIG. 13B-6 illustrates the last step of the example process. Drive lineconnection 1307 can be formed inside vias 1309 and across TFE2 1319.Drive line connection 1307 can be formed of ITO or IZO, for example.Finally, thin film layer TFE3 1323 can be deposited over the materialstack. As shown, drive line segments 1301 can be electrically connectedto each other through vias 1309 and drive line connection 1307. Driveline segments 1301 can be electrically isolated from sense line 1303 byisolation slits 1310. By way of the above-described process, thefabrication of the drive and sense line structure of FIG. 3A, over OLEDlayers, can be accomplished.

Because the cathode layer (or the anode layer in the case of invertedOLED displays) of the touch screen of this disclosure can be formed overLED layers such as OLED layers, it can be preferable for the cathodelayer (or the anode layer) to be transparent. Thus, it can be necessaryto make the cathode layer thin. This, in turn, can cause the sheetresistance of the cathode layer to be high. High resistance coupled withthe various capacitances inherent in the OLED material stack can resultin increased voltage delay in drive lines, for example. Therefore,reducing the sheet resistance of the cathode layer can be desired. FIGS.14A and 14B illustrate an exemplary way of lowering the sheet resistanceof the cathode layer according to examples of the disclosure. FIGS. 14Aand 14B show a top-view of the drive and sense line structure of FIG. 3Aover OLED layers 1405. Drive line connections 1407 can correspond toanode connections 1107 or 1207, or drive line connection 1307. Extralines 1421 can be formed as a mesh-like structure across drive linesegments 1401 and sense line 1403, and can be formed in between OLEDlayers 1405 so as not to obstruct the light emitted from OLED layers.Extra lines 1421 can be electrically connected to the cathode layer byway of vias 1409. Because extra lines 1421 can be formed between OLEDlayers 1405, extra lines need not be as transparent as the cathode layerthat can form drive line segments 1401 and sense line 1403. Therefore,extra lines 1421 can be thicker than the cathode layer, or can be formedof a different, lower resistance, material than the cathode layer, orboth. The effective sheet resistance of the cathode layer can thereforebe reduced without affecting the transparency of the cathode layer(i.e., drive line segments 1401 and sense line 1403).

Using the processes of FIG. 11, 12, or 13, extra lines 1421 can beformed of the same material and at the same time as anode connections1107 or 1207, or drive line connection 1307. FIG. 14A shows an examplewith a single drive line connection 1407 between adjacent drive linesegments 1401. FIG. 14B shows an example with two drive line connections1407 between adjacent drive line segments 1401. More drive lineconnections 1407 can be used in accordance with the examples of thedisclosure.

Sometimes, it can be preferable or necessary to connect adjacent driveline segments by way of drive line connections that overlap the LEDlayers of the touch screen. This can be the case, for example, in highdensity AMOLED displays where there is minimal space between adjacentOLED layers. FIGS. 15A and 15B illustrate an exemplary process forforming a drive line connection over OLED layers according to examplesof the disclosure. FIG. 15A shows a top-view of a patterned cathodestructure 1550 in accordance with the examples of this disclosure. Driveline segments 1501 can be on either side of sense line 1503, and can beelectrically isolated from sense line by isolation slits 1510. Bothdrive line segments 1501 and sense line 1503 can be formed of cathode1011 of FIG. 10. OLED layers 1505 can be underneath drive line segments1501 and sense line 1503, and can correspond to OLED layers 1009 of FIG.10. Drive line segments 1501 can be electrically connected to each otherby way of drive line connection 1507. Drive line connection 1507 canpartially overlap OLED layers 1505, and it can therefore be preferablefor drive line connection 1507 to be substantially transparent. Driveline connection 1507 can be formed of ITO or IZO, for example. Driveline connection 1507 can be electrically connected to drive linesegments 1501 by way of vias 1509. The process steps for fabricating thepatterned cathode structure 1550 of FIG. 15A will be described withreference to FIG. 15B, which illustrates a cross-sectional view ofcross-section X-Y at each process step.

FIG. 15B-1 illustrates the first step of the example process. Anodes1506 can be formed on PLN 1511. Anodes 1506 can correspond to anodes1007 in FIG. 10. OLED layers 1505 can be formed on anodes 1506. OLEDlayers can correspond to OLED layers 1009 in FIG. 10. Anode 1506 andOLED layer 1505 stacks can be electrically isolated from each other byorganic passivation 1513. Organic passivation can correspond to PDL 1005in FIG. 10. Cathode 1515 can be blanket deposited over the materialstack, and can correspond to cathode 1011 in FIG. 10.

FIG. 15B-2 illustrates the next step of the example process. A thin filmencapsulation layer TFE1 1517 can be formed on cathode 1515. TFE1 1517can protect OLED layers 1505 from the next steps in the process.

FIG. 15B-3 illustrates the next step of the example process. TFE1 1517can be etched to partially open isolation slits 1510. OLED layers 1505can be protected from the etching of TFE1 1517 at isolation slits 1510because the coverage of TFE1 over OLED layers can protect OLED layers.

FIG. 15B-4 illustrates the next step of the example process. Cathode1515 can be etched to complete the opening of isolation slits 1510. Withthe etching of cathode 1515 in this step, drive line segments 1501 andsense line 1503 can be defined. Drive line segments 1501 can beelectrically isolated from sense line 1503 by organic passivation 1513and because of the removal of conductive cathode 1515 material betweendrive line segments and sense line. As described above, OLED layers 1505can be protected from the etching of cathode 1515 because the coverageof TFE1 1517 over OLED layers can protect OLED layers.

FIG. 15B-5 illustrates the next step of the example process. Thin filmencapsulation layer TFE2 1519 can be deposited, and vias 1509 can beetched in TFE1 1517 and TFE2 to allow for electrical connection tocathode 1515.

FIG. 15B-6 illustrates the last step of the example process. Drive lineconnection 1507 can be formed inside vias 1509 and across TFE2 1519. Asshown, drive line segments 1501 can be electrically connected to eachother through vias 1509 and drive line connection 1507. Drive linesegments 1501 can be electrically isolated from sense line 1503 byisolation slits 1510 and organic passivation 1513. By way of theabove-described process, the fabrication of the drive and sense linestructure of FIG. 3A, over OLED layers, can be accomplished.

Instead of blanket depositing the cathode layer, and then subsequentlyetching it to provide isolation for the drive and sense segments of theexamples of this disclosure, the cathode layer can be deposited by wayof a shadow mask. FIGS. 16A and 16B illustrate an exemplary process forperforming shadow mask deposition of the cathode layer according toexamples of this disclosure. FIG. 16A shows a top-view of the process ofdepositing a cathode layer, corresponding to drive line segments 1601and sense lines 1603, by using a shadow mask. A shadow mask allows forselective deposition of a material on a surface by way of a physicalmask placed between the source of the material being deposited and thesurface onto which the material is being deposited. Areas in the maskwith holes or openings allow for the material to pass through anddeposit on the surface. Areas in the mask without holes or openingsprevent the material from passing through, and therefore no material isdeposited at the corresponding area on the surface. FIG. 16A shows thedeposition of drive line segments 1601 and sense lines 1603 using threeshadow masks. More or fewer shadow masks can be used in accordance withthis example. Further, it is understood that while the drive and senseline structure of FIG. 3A is illustrated, the drive and sense linestructure of FIG. 3B can be similarly formed.

FIG. 16A-1 illustrates the first step of the example process. Alternaterows of drive line segments 1601 can be deposited by way of a shadowmask having openings corresponding to the positioning of drive linesegments on the surface of the touch screen. FIG. 16A-2 illustrates thenext step of the example process. Sense lines 1603 can be deposited byway of a shadow mask as described above. FIG. 16A-3 illustrates the laststep of the example process. The remaining alternate rows of drive linesegments 1601 can be deposited by way of a shadow mask as describedabove. Finally, a thin film encapsulation layer can be blanket deposited(not shown in FIG. 16A) over drive line segments 1601 and sense line1603 to encapsulate the material stack. As described throughout thisdisclosure, it can be necessary to electrically connected adjacent driveline segments 1601 by way of drive line connections 1607 to form drivelines, such as drive lines 222 of FIG. 3A. In this example, drive lineconnections 1607 can be formed prior to shadow mask deposition of driveline segments 1601 and sense line 1603. FIG. 16B illustrates across-sectional view of cross-section X-Y during the process steps ofFIG. 16A to better show drive line connections 1607.

FIG. 16B-1 illustrates the first step of the example process. Drive lineconnection 1607 can be formed on PLN 1611. Drive line connection 1607can correspond to anode connections 1107 or 1207, for example. Organicpassivation 1613 can be formed on drive line connection 1607 and PLN1611, and can be etched at vias 1609 to allow for electrical connectionto drive line connection. OLED layers 1605 (not shown in FIG. 16B) canbe formed in other areas of the touch screen. Drive line segment 1601portion of cathode 1615 can be deposited by shadow mask. It is notedthat no need exists to further etch cathode 1615 to form drive linesegment 1601 portion of cathode because shadow mask deposition can allowfor pre-patterned deposition of cathode.

FIG. 16B-2 illustrates the next step of the example process. Sense line1603 portion of cathode 1615 can be deposited by shadow mask. Sense line1603 and drive line segments 1601 can be electrically isolated from eachother because no electrical connection can exist between them, whetherin cathode 1615 or by drive line connection 1607. It is noted that noneed exists to further etch cathode 1615 to form sense line segment 1603portion of cathode for the reasons described above.

FIG. 16B-3 illustrates the last step of the example process. A thin filmencapsulation layer TFE1 1617 can be formed on drive line segment 1601and sense line 1603 portions of cathode 1615. By way of theabove-described process, the fabrication of the drive and sense linestructure of FIG. 3A, over OLED layers, can be accomplished. Further,the shadow mask deposition process of FIG. 16 allows for nophotolithography or etching process steps after the formation of OLEDlayers 1605, which can help to prevent damage to OLED layers on thetouch screen.

Alternatively to shadow mask deposition, laser ablation can be performedto form the drive and sense segments of the examples of this disclosure.FIGS. 17A and 17B illustrate an exemplary process for performing laserablation to form drive and sense segments according to examples of thedisclosure. FIG. 17A shows a top-view of a process for defining driveline segments 1701 and sense lines 1703 on the surface of the touchscreen. FIG. 17A-1 illustrates the first step of the example process.Cathode 1715 can be blanket deposited over the surface of the touchscreen. FIG. 17A-2 illustrates the second step of the process. Cathode1715 can be laser patterned to scribe out portions of cathode 1715 toform drive line segments 1701 and sense lines 1703 such thatsubstantially no cathode material exists between drive line segments andsense lines. Finally, a thin film encapsulation layer can be blanketdeposited (not shown in FIG. 17A) over drive line segments 1701 andsense lines 1703 to encapsulate the material stack. As describedthroughout this disclosure, it can be necessary to electrically connectadjacent drive line segments 1701 by way of drive line connections 1707to form drive lines, such as drive lines 222 of FIG. 3A. In thisexample, drive line connections 1707 can be formed prior to thedeposition, and the laser ablation, of cathode 1715 to form drive linesegments 1701 and sense lines 1703. FIG. 17B illustrates across-sectional view of cross-section X-Y during the process steps ofFIG. 17A to better show drive line connections 1707.

FIG. 17B-1 illustrates the first step of the example process. Drive lineconnection 1707 can be formed on PLN 1711. Drive line connection 1707can correspond to anode connections 1107 or 1207, for example. Organicpassivation 1713 can be formed on drive line connection 1707 and PLN1711, and can be etched at vias 1709 to allow for electrical connectionto drive line connection. OLED layers 1705 (not shown in FIG. 17B) canbe formed in other areas of the touch screen. Cathode 1715 can beblanket deposited over the material stack.

FIG. 17B-2 illustrates the next step of the example process. Cathode1715 can be laser patterned to form drive line segment 1701 and senseline 1703 portions of cathode. Drive line segments 1701 and sense line1703 can be electrically isolated from each other because no electricalconnection can exist between them, whether in cathode 1715 or by driveline connection 1707. Further, the laser energy used during the laserpatterning can be regulated to avoid damage to the material stack belowcathode 1715, including organic passivation 1713.

FIG. 17B-3 illustrates the last step of the example process. A thin filmencapsulation layer TFE1 1717 can be formed on drive line segment 1701and sense line 1703 portions of cathode 1715. By way of theabove-described process, the fabrication of the drive and sense linestructure of FIG. 3A, over OLED layers, can be accomplished.

Because the drive line segments and sense lines of the examples of thedisclosure can operate as a cathode for a pixel circuit during a displayphase of the touch screen, it can be beneficial to ensure that the driveline segments and the sense lines properly cover the LED emissionlayers, such as OLED emission layers, in the touch screen. Therefore, inany of the fabrication procedures described above, it can be preferableto modify the distance between adjacent OLED emission layers to ensureproper cathode layer coverage of the OLED emission layers. FIGS. 18A-18Dillustrate an exemplary process for modifying the distance betweenadjacent OLED emission layers according to examples of the disclosure.

FIGS. 18A and 18B illustrate why OLED emission layer distancemodification can be necessary. FIG. 18A shows a top-view of a portion ofa touch screen according to examples of the disclosure. Drive linesegment 1801 can be adjacent to sense line 1803. OLED layers 1805 can becovered by drive line segment 1801 and sense line 1803, which can act asa cathode for OLED layers during a display phase of the touch screen.

FIG. 18B shows a zoomed-in view of the area between drive line segment1801 and sense line 1803. Drive line segment 1801 can be formed overOLED layer 1805, which can be formed over anode 1807. Sense line 1803can be formed over OLED layer 1805, which can be formed over anode 1807.OLED distance 1825 can be the distance between adjacent OLED layers1805. Isolation width 1827 can be the distance between adjacent portionsof cathode 1815, i.e., the distance between drive line segment 1801 andsense line 1803. Minimum anode overlap 1829 can be the minimum distancethat the edge of anode 1807 needs to extend over the edge of OLED layer1805 for desired OLED operation. Minimum cathode overlap 1831 can be theminimum distance that the edge of cathode 1815 needs to extend over theedge of OLED layer 1805 for desired OLED operation. If the fabricationsteps of forming drive line segment 1801 and sense line 1803 provide noadditional constraints to those provided above, then isolation width1827 can be reduced to almost zero, and OLED distance 1825 can beslightly larger than twice minimum cathode overlap 1831. OLED distance1825 cannot be reduced to exactly twice minimum cathode overlap 1831because it is desired that drive line segment 1801 and sense line 1803be electrically isolated from each other for proper touch screenoperation; reducing OLED distance to twice minimum cathode overlap wouldmean that isolation width would be zero, which would mean that driveline segment 1801 and sense line 1803 would be touching, and thus notelectrically isolated from each other.

Sometimes the process for fabricating drive line segment 1801 and senseline 1803 can provide a constraint as to how close drive line segmentand sense line can be formed. That is to say, the fabrication processutilized might provide for a minimum distance between drive line segment1801 and sense line 1803 that is greater than the minimum distancedescribed above. For example, photolithography and etching can have aminimum resolution limit, or shadow mask deposition can have a minimummask aperture limit. In cases such as these, it can desirable to adjustthe spacing of adjacent OLED layers 1805 only at the edges of drive linesegment 1801 and sense line 1803 so that the spacing of OLED layers inother areas of the touch screen, and thus the general OLED aperture(i.e., the spacing between OLED pixels), can be left unchanged.

FIG. 18C illustrates one way to reduce the spacing of OLED layers at theedges of touch segments (i.e., drive line segments and sense lines). Thetouch screen 1800 can include a plurality of OLED pixel banks 1802. Eachpixel bank can include a plurality of OLED layers 1805; in this example,it could be three: one OLED layer each for red light, green light, andblue light. The touch screen can also include a plurality of touchsegments 1801 overlaying the pixel banks 1802. The touch segments 1801can correspond to drive line segments 301 and sense lines 223 of FIG.3A, for example. Touch segments 1801 can be separated from each other byisolation width 1827. To accommodate the minimum necessary isolationwidth 1827, as described above, the dimensions of OLED layers 1805adjacent to touch segment 1801 boundaries can be modified. For example,the right-most OLED layer 1805 in a pixel bank 1802 B can have its sizereduced in the x-direction to accommodate the minimum required isolationwidth 1827, as shown. The dimensions of all of the OLED layers 1805 in apixel bank 1802 C can be reduced in the y-direction for the same reasonas above. Such modifications can be made to the remaining pixel banks1802 as needed. However, pixel bank 1802 A need not be modified becausepixel bank A, as defined, is not adjacent to a touch segment 1801boundary. By proceeding with the modifications of the pixel banks 1802as described above, the general spacing between, and the size of, mostOLED layers 1805 on the touch screen 1800 can remain unchanged whileallowing for the accommodation of a minimum isolation width 1827 asdictated by process parameters. The process steps for modifying theeffective dimensions of certain OLED layers will be described withreference to the cross-sectional view of cross-section X-Y of FIG. 18C.

FIG. 18D illustrates a process to reduce the dimensions of touch segmentboundary OLED layers without the need to modify the shadow mask used todeposit the OLED layers. FIG. 18D-1 illustrates the first step of theexample process. Anodes 1806 can be formed on PLN 1811. Anodes 1806 cancorrespond to anodes 1007 in FIG. 10, for example. Organic passivation1813 can be formed between anodes 1806, and can correspond to PDL 1005in FIG. 10, for example. OLED layers 1805 can be deposited by shadowmask (the concept of shadow mask deposition was described previously).Anode 1806 and OLED layer 1805 stacks can be electrically isolated fromeach other by organic passivation 1813.

Reduced OLED layer 1807 can be at the boundary of touch segment 1801,and can be deposited with the same shadow mask as OLED layers 1805.However, during the formation of organic passivation 1813, enlargedorganic passivation 1814 at the boundary of touch segment 1801 can beformed to extend towards reduced OLED layer 1807. Therefore, duringshadow mask deposition of OLED layers 1805, reduced OLED layer 1807 canbe partially formed on anode 1806 and enlarged organic passivation 1814.The portion of reduced OLED layer 1807 that is formed on enlargedorganic passivation 1814 can correspond to the desired reduction, in thex-direction, of reduced OLED layer.

FIG. 18D-2 illustrates the next step of the example process. Touchsegments 1801 can be deposited by shadow mask, and can be isolated fromeach other by isolation width 1827.

FIG. 18D-3 illustrates the last step of the example process. Thin filmencapsulation layer TFE 1817 can be deposited over the material stack.The portion of reduced OLED layer 1807 that is not in contact with anode1806 may not contribute to the light emitted from reduced OLED layerbecause it is not in contact with anode. Therefore, touch segment 1801need not overlap the entirety of reduced OLED layer 1807, but only theportion of reduced OLED layer that is in contact with anode 1806.Accordingly, the effective dimension of reduced OLED layer 1807 can besmaller than that of OLED layers 1805. In the way described above, thedimensions of touch segment boundary OLED layers can be reduced withoutthe need to modify the shadow mask used to deposit the OLED layers.

Although the above process has been described only with reference tomodifying the dimensions of LED layers, such as OLED layers, at theboundaries of touch segments, the dimensions of OLED layers adjacent todrive line connections can similarly be modified. For example, more areacan be provided for drive line connection 1807 by modifying thedimensions of OLED layers 1805 that are adjacent to drive lineconnection in the manner described with reference to FIGS. 18C and 18D.

Although examples of this disclosure have been fully described withreference to the accompanying drawings, it is to be noted that variouschanges and modifications will become apparent to those skilled in theart. Such changes and modifications are to be understood as beingincluded within the scope of examples of this disclosure as defined bythe appended claims.

Therefore, according to the above, some examples of the disclosure aredirected to a touch screen comprising a transistor layer, a first layerdisposed over the transistor layer and configured to operate as alight-emitting diode (LED) cathode during a display phase and as touchcircuitry during a touch sensing phase, and an LED layer disposedbetween the transistor layer and the first layer. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the LED layer comprises an organic light-emitting diode (OLED)layer. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the transistor layer comprises afirst transistor connected to the LED layer, and a power supply lineconnected to the first transistor. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, during thedisplay phase, the power supply line voltage is set to a first voltage,and during the touch sensing phase, the power supply line voltage is setto a second voltage. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the first voltage causes theLED layer to emit light, and the second voltage causes the LED layer tonot emit light. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the touch screen furthercomprises a second transistor connected to the first transistor, and agate voltage line connected to a gate terminal of the second transistor,wherein during the display phase, the gate voltage line is set to afirst voltage, and during the touch sensing phase, the gate voltage lineis set to a second voltage. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, the first voltagecauses the second transistor to turn on, and the second voltage causesthe second transistor to turn off. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, the firstlayer comprises a plurality of drive lines and a plurality of senselines. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, a drive line comprises a first driveline segment, and a second drive line segment electrically connected tothe first drive line segment by a drive line connection.

Some examples of the disclosure are directed to a method for operating atouch screen comprising operating, during a display phase, a first layeras a cathode of a light-emitting diode (LED) layer, and operating,during a touch sensing phase, the first layer as touch circuitry.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, operating the first layer as the cathode of theLED layer comprises operating the first layer as the cathode of anorganic light-emitting diode (OLED) layer. Additionally or alternativelyto one or more of the examples disclosed above, in some examples,operating the first layer as the cathode of the LED layer comprisessetting the voltage of a power supply line connected to a transistor toa first voltage that causes the LED layer to emit light, and operatingthe first layer as touch circuitry comprises setting the voltage of thepower supply line to a second voltage that causes the LED layer to notemit light. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, operating the first layer as touchcircuitry comprises operating the first layer as a plurality of driveline segments and a plurality of sense lines, and electricallyconnecting a first drive line segment to a second drive line segment.

Some examples of the disclosure are directed to a method for fabricatinga light-emitting diode (LED) touch screen, the method comprising forminga plurality of LED layers, and forming, over the LED layers, a pluralityof regions of a first layer configurable to operate as a plurality ofLED cathodes during a display phase and as touch circuitry during atouch sensing phase. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, forming the plurality of LEDlayers comprises forming a plurality of organic light-emitting diode(OLED) layers. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, forming the plurality ofregions of the first layer comprises depositing the first layer over theLED layers, and removing portions of the first layer to form regions ofthe first layer. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, forming the plurality ofregions of the first layer comprises depositing the first layer over theLED layers, and oxidizing portions of the first layer to form regions ofthe first layer. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the method further comprisesdepositing a second layer over the first layer, and removing portions ofthe second layer to form regions of the second layer, wherein the secondlayer protects the LED layer from the removal of portions of the firstlayer and the second layer. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, removing portions ofthe first layer and the second layer comprises etching portions of thefirst layer and the second layer. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, removingportions of the first layer comprises laser ablating portions of thefirst layer. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, forming the plurality ofregions of the first layer comprises depositing the first layer using ashadow mask. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the method further comprisesmodifying the dimensions of an LED layer at a boundary of one of theplurality of regions of the first layer. Additionally or alternativelyto one or more of the examples disclosed above, in some examples,forming the plurality of regions of the first layer comprises forming,of the first layer, a plurality of drive line segments and a pluralityof sense lines, and electrically connecting a first drive line segmentto a second drive line segment using a drive line connection.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the method further comprises forming the driveline connection over the first layer. Additionally or alternatively toone or more of the examples disclosed above, in some examples, themethod further comprises forming the drive line connection under thefirst layer.

The invention claimed is:
 1. A touch screen comprising: a transistorlayer including a first transistor and a second transistor connected tothe first transistor; a first layer disposed over the transistor layerand configured to operate as a light-emitting diode (LED) cathode duringa display phase and as touch circuitry during a touch sensing phase; anLED layer disposed between the transistor layer and the first layer,wherein the first transistor is connected to the LED layer and a powersupply line; and a gate voltage line connected to a gate terminal of thesecond transistor, wherein during the display phase, the gate voltageline is set to a first voltage, which causes the second transistor toturn on, and during the touch sensing phase, the gate voltage line isset to a second voltage, which causes the second transistor to turn off.2. The touch screen of claim 1, wherein the LED layer comprises anorganic light-emitting diode (OLED) layer.
 3. The touch screen of claim1, wherein during the display phase, the power supply line voltage isset to a first power supply voltage, and during the touch sensing phase,the power supply line voltage is set to a second power supply voltage,different than the first power supply voltage.
 4. The touch screen ofclaim 3, wherein the first power supply voltage causes the LED layer toemit light, and the second power supply voltage causes the LED layer tonot emit light.
 5. The touch screen of claim 1, wherein the first layercomprises a plurality of drive lines and a plurality of sense lines. 6.The touch screen of claim 5, wherein a drive line comprises: a firstdrive line segment; and a second drive line segment electricallyconnected to the first drive line segment by a drive line connection. 7.The touch screen of claim 6, wherein the drive line connection isdisposed over the first layer.
 8. The touch screen of claim 6, whereinthe drive line connection is disposed under the first layer.
 9. Thetouch screen of claim 1, wherein the second transistor is connected tothe first transistor in series.
 10. The touch screen of claim 1, whereinthe first voltage causes the LED layer to emit light, and the secondvoltage causes the LED layer to not emit light.
 11. A method foroperating a touch screen comprising: operating, during a display phase,a first layer as a cathode of a light-emitting diode (LED) layer bysetting a voltage of a gate voltage line to a first voltage, the gatevoltage line connected to a gate terminal of a second transistor that isconnected to a first transistor, the first transistor connected to theLED layer and a power supply line, and the first voltage causing thesecond transistor to turn on; and operating, during a touch sensingphase, the first layer as touch circuitry by setting the voltage of thegate voltage line to a second voltage, the second voltage causing thesecond transistor to turn off.
 12. The method of claim 11, wherein:operating the first layer as the cathode of the LED layer comprisessetting a voltage of the power supply line connected to a transistor toa first power supply voltage that causes the LED layer to emit light,and operating the first layer as the touch circuitry comprises settingthe voltage of the power supply line to a second power supply voltage,different from the first power supply voltage, that causes the LED layerto not emit light.
 13. The method of claim 11, wherein operating thefirst layer as the touch circuitry comprises: operating the first layeras a plurality of drive line segments and a plurality of sense lines;and electrically connecting a first drive line segment to a second driveline segment using a drive line connection.
 14. The method of claim 13,wherein the drive line connection is disposed over the first layer. 15.The method of claim 13, wherein the drive line connection is disposedunder the first layer.
 16. The method of claim 11, wherein the secondtransistor is connected to the first transistor in series.
 17. Themethod of claim 11, wherein the first voltage causes the LED layer toemit light, and the second voltage further the LED layer to not emitlight.